When Patrick Murphy was 6, he became obsessed with vacuum cleaners. The boy, who has autism, used to slip out of his house near Buffalo without telling his parents, running to a nearby appliance store or into strangers’ homes to marvel at vacuum cleaners. Patrick is now 14, and his parents have double bolts on the doors in their home and brackets on their windows. Still, Patrick — who is now focused on dogs — manages to sneak out. Two weeks ago, he crept from the house after his mother went to bed. When his father came home, he alerted the police. They found Patrick running barefoot in his pajamas at 2 a.m., three miles from his home.